The primary research question of the proposed study is this: Is a combination water-based physical exercise + cognitive training program for older veterans with amnestic Mild Cognitive Impairment (MCI) feasible? The primary aims of the proposed research are: 1) demonstrate adequate recruitment and retention rates; 2) refinement of inclusion/exclusion criteria; and 3) further refine the combination water- based physical exercise + cognitive training (WATER+CT) intervention. These aims will be tested in a two-phase clinical trial with a single group design: 1 exercise training phase and 2) a cognitive training phase. The exercise training phase consists of a water-based physical exercise program that emphasizes cardiovascular fitness and strength training through a combination of non-weight bearing exercises that include land-based stretching and water-based activities. This 2-year pilot project will include 50 veterans diagnosed with amnestic MCI age 50-90. The exercise component consists of a six-month water-based exercise program followed by a four-week cognitive training program. For the first two months of the water-based exercise program, veterans will come to thrice-weekly group sessions at Aquatic Therapy Center at the VA Palo Alto Health Care System. This will transition to a self-paced exercise program for the remaining four months. After completion of the exercise program, veterans will begin classroom-based cognitive training at the VAPAHCS. The cognitive training is based on an efficacious cognitive program that is structured around two components, pre-training and mnemonic training, both of which have been used successfully in persons with aMCI. Assessments of adherence will be administered throughout treatment and measures of feasibility will be completed post-treatment. Participants will complete a variety of neuropsychological measures taping into areas of cognition such as attention, executive functioning, and memory. To study possible predictors of treatment response, we will also collect biological (cardiovascular functioning and BDNF plasma levels) and genetic data (APOE and BDNF genotypes) from these participants. We hope to provide initial evidence of the feasibility of a water- based exercise training augmentation for cognitive training thus laying the groundwork for full-scale clinical trials targeting the lessening of cognitive impairment in person with amnestic MCI by non-pharmacological means.